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Homework 1 Attempts

B is better. The density of the two kinds of stones, A and B, is similar, and the saturated water coefficient of A is larger than that of B, so the frost resistance of B is better.

2. The mechanical indexes of stone are: uniaxial compressive strength, uniaxial compressive deformation, splitting strength, shear strength, point load strength, flexural strength, and Los Angeles abrasion rate.

The mechanical indexes of aggregate are: crushing value, polishing value, impact value, and wear value.

3. Classification according to material source: gravel, gravel classification according to density: light aggregate, heavy aggregate

According to the particle size classification: more than 4.75mm is coarse aggregate, less than 4.75mm is fine aggregate

Classification by chemical composition: SiO2 content is greater than 65%, acidic aggregate; SiO2 content less than 52%, alkaline aggregate; Content between 52%-65%, neutral aggregate.

4. Crushing value: A>B, so B hardness is greater and the bearing capacity is better.

Polishing value: A>B, so the slip resistance of A is better.

Abrasion value: A>B, so A's anti-abrasion performance is better.

5. True density: the true volume mass of the solid unit of stone minerals $ρ_{} = \frac{m_{}}{V_{}}$

Apparent density: the mass of the gross volume per unit of stone mineral entities, $ρ_{} = \frac{m_{}}{V_{} + V_{}}$ including closed pores

Gross volume density: the mass per unit gross volume of stone mineral entities, $ρ_{} = \frac{m_{}}{V_{} + V_{} + V_{}}$ including pores

Surface dry density: the saturated surface dry mass including the total pore volume of the aggregate mineral entity $ρ_{} = \frac{m_{}}{V_{} + V_{} + V_{}}$

Packing density: The mass of the aggregate granular mineral entity per unit of filling volume $ρ= \frac{m_{}}{V_{} + V_{} + V_{} + V_{}}$

Sorting: $真密度$ > apparent density> gross bulk density> superficial dry density> filling density

6.A. Intermittent gradation, the structural form of the mixture is a skeleton dense structure.

B. Continuous gradation, the structure of the mixture is a suspended dense structure.

C. Open gradation, the structure of the mixture is a skeleton void structure.

7. Grading: particle size and particle size distribution, which refers to the proportion of aggregate particles in the range of particle size to be determined by mass or weight.

Fineness modulus: an index that characterizes the thickness of the particle size of natural gravel.

A and B fineness modulus are the same, and the gradation is not necessarily the same.

10. PCC is made of spherical smooth aggregate (gravel), and the angular coefficient is too large to affect its working performance.

HMA uses rough angular aggregates (crushed stone), which have high friction between particles and good anti-slip performance. At the same time, the rough surface is conducive to increasing the contact area with asphalt, so that the aggregate adheres more closely with asphalt.

11 $密度： \frac{5227}{5227−3295} =2.705g/ {cm}^{}$ . Gross bulk density: $： \frac{5216}{5227−3295} =2.7g/ {cm}^{}$ Apparent

Moisture $： \frac{5227−5216}{5216} ∙100%=0.2%$ content water absorption $性： \frac{5298−5216}{5216} ∙100%=1.5%$

9. (1) Calculate the sub-counting screening residue rate of each aggregate and the median value of the required gradation and the sub-counting screening residue

class Particle size	9.5-19	4.75-9.5	2.36-4.75	Sand	stuffing	Median theoretical grading	Grading and sub-counting sieve remains
19
16.5	13.1					96.5	3.5
13.2	28.5					83	13.5
9.5	46.2	14.5				67	16
4.75	12.2	81.3	3.2	7.4		42	25
2.36		4.2	85.9	9.1		30	12
1.18			10.9	10.1		22	8
0.6				31.9		16	6
0.3				31.0	3.6	12	4
0.15				7.8	4.4	8	4
0.075				2.7	12.0	6	2

(2) Assuming that the dosage percentage of various aggregates is X₁,_{X 2}, X₃, Y, Z, then there is X₁+X ₂+X₃+Y+Z=100

Where:_{X 1}: 9.5-19 Crushed Stone X₂: 4.75-9.5 Crushed Stone X₃: 2.36-9.75 Crushed Stone Y: Fine Sand Z: Filler

（3）X₁= $\frac{17}{13.1+28.5} ×100$ =40.9 Z= $\frac{6}{80} ×100$ =7.5 Y= $\frac{6}{31.9} ×100$ =18.8

Let's assume that 2.36mm particles are provided by 2.36-4.75 crushed stone (as this is the most passable material).

则 X₃= $\frac{12}{85.9} ×100$ =14.0X2 = 1-(X₁+ X₃+Y+Z）=18.8

(4) Find the synthetic gradation

Mesh size	9.5-19 Gravel			4.75-9.5 Crushed stone			2.36-4.75 gravel
Mesh size		The original grading is divided into sieve remains	Dosage ratio	Percentage of mixture	The original grading is divided into sieve remains	Dosage ratio	Percentage of mixture	The original grading is divided into sieve remains	Dosage ratio	Percentage of mixture
19		40.9			18.8			14.0
16.5	13.1			5.4
13.2	28.5			11.7
9.5	46.2			18.9		14.5			2.7
4.75	12.2			5.0		81.3			15.3	3.2	0.4
2.36						4.2			0.8	85.9	12.0
1.18										10.9	1.5
0.6
0.3
0.15
0.075

Mesh size	Sand			stuffing
Mesh size		The original grading is divided into sieve remains	Dosage ratio	Percentage of mixture	The original grading is divided into sieve remains	Dosage ratio	Percentage of mixture
19		18.8			7.5
16.5
13.2
9.5
4.75	7.4			1.4
2.36	9.1			1.7
1.18	10.1			1.8
0.6	31.9			6.0
0.3	31.0			5.8		3.6		0.3
0.15	2.7			0.5		4.4		0.3
0.075						12.0		0.9

Mesh size	Synthetic gradation		Theoretical gradation range
Mesh size		Divide the sieve surplus	Theoretical gradation range	Pass rate
19		100	100
16.5	5.4	94.6	93~100
13.2	11.7	82.9	78~88
9.5	21.6	61.3	62~72
4.75	22.1	39.2	37~47
2.36	14.5	24.7	25~35
1.18	3.3	21.4	18~26
0.6	6.0	15.4	13~19
0.3	6.1	9.3	9~15
0.15	0.8	8.5	6~10
0.075	0.9	7.6	5~7

（5）It can be seen 9.5mm, 2.36mm, 0.075mm The range is unqualified and the dosage needs to be adjusted.

Reduce 9.5-19 gravel by 3% and increase the amount of stone chips by 3%.

Mesh size	9.5-19 Gravel			4.75-9.5 Crushed stone			2.36-4.75 gravel
Mesh size		The original grading is divided into sieve remains	Dosage ratio	Percentage of mixture	The original grading is divided into sieve remains	Dosage ratio	Percentage of mixture	The original grading is divided into sieve remains	Dosage ratio	Percentage of mixture
19		37.9			18.8			14.0
16.5	13.1			5.0
13.2	28.5			10.8
9.5	46.2			17.5		14.5			2.7
4.75	12.2			5.4		81.3			15.3	3.2	0.4
2.36						4.2			0.8	85.9	12
1.18										10.9	1.3
0.6
0.3
0.15
0.075

Mesh size	Sand			stuffing
Mesh size		The original grading is divided into sieve remains	Dosage ratio	Percentage of mixture	The original grading is divided into sieve remains	Dosage ratio	Percentage of mixture
19		21.8			7.5
16.5
13.2
9.5
4.75	7.4			1.6
2.36	9.1			2.0
1.18	10.1			2.2
0.6	31.9			7
0.3	31.0			6.7		3.6		0.3
0.15	2.7			0.7		4.4		0.4
0.075						12.0		0.9

Mesh size	Synthetic gradation		Theoretical gradation range
Mesh size		Divide the sieve surplus	Theoretical gradation range	Pass rate
19		100	100
16.5	5.0	95	93~100
13.2	10.8	84.2	78~88
9.5	20.2	64	62~72
4.75	22.7	41.3	37~47
2.36	14.8	26.5	25~35
1.18	3.5	23	18~26
0.6	7	16	13~19
0.3	7	9	9~15
0.15	1.1	7.9	6~10
0.075	0.9	7	5~7